Deterioration of an individual's rotator cuff may lead to the need to undergo a shoulder arthroplasty procedure. In severe cases, a person's humeral head may translate in a more superior direction during abduction of their effected arm resulting in the superior surface of the humeral head articulating with both the inferior surface of the acromion and the acromioclavicular joint. Articulation between these two bones could lead to accelerated destruction of the humeral head and erosion of the acromion and the acromioclavicular joint.
It was generally accepted practice for orthopedic surgeons to treat individuals with compromised rotator cuffs using standard sized shoulder stem prosthesis with oversized humeral heads to reestablish the joint space created by the bone loss. Humeral head bipolar prostheses have also been utilized by surgeons to address the stability problems associated with rotator cuff tear arthropathy. Both of these treatment modalities led to the overstuffing of the joint space and a resultant reduced range of motion for the effected arm of the individual. Several non-implant surgical techniques have been used with limited success in an attempt to address the rotator cuff tear arthropathy, including surgically smoothing the greater tubercle. Unfortunately, the individual still experienced reduced range of motion and joint pain because of the bone on bone contact.
Recent developments in the shoulder arthroplasty field involve the design of modular humeral heads that are configured to include a glenoid bearing portion and an extended acromion bearing portion. Problems that have been seen with these types of designs is excessive post-operative translation in the superior direction because of the previous bone loss and the use of a single radius of curvature for the two bearing portions. Another problem encountered with the extended bearing modular humeral heads is the head being incorrectly rotated when the prosthesis is assembled in the operating room. The malrotation may cause the humeral head to be positioned in a less then optimal location relative to the acromion during arm abduction.